Frequency of misdiagnosis in hypertrophic cardiomyopathy

Background and aims: Hypertrophic cardiomyopathy (HCM) is characterized by unexplained left ventricular hypertrophy (LVH) ≥15 mm. The condition is often hereditary, and family screening is recommended to reduce the risk of adverse disease complications and premature death among relatives. Correct diagnosis of index patients is important to ensure that only relatives at risk of disease development are invited for family screening. To investigate whether patients with International Classification of Disease, Tenth Revision (ICD-10) codes for HCM (DI421) or hypertrophic obstructive cardiomyopathy (HOCM) (DI422) fulfilled recognized diagnostic criteria. Methods: All patients with ICD-10 codes for HCM or HOCM at a Department of Cardiology were identified and had their diagnosis validated by a cardiac investigation or a review of their medical records and previous investigations. Results: A total of 240 patients had ICD-10 codes for HCM/HOCM, of whom 202 (84%, 202/240) underwent re-examination, while 38 (16%, 38/240) had their hospital notes reviewed. A total of 76 patients (32%, n = 76/240) did not fulfil diagnostic criteria, of whom 39 (51%, n = 39/76) had normal (10 mm) or modest LV wall thickness (11-14 mm). The remaining 37 patients (49%, n = 37/76) had LVH ≥15 mm, which was well explained by uncontrolled hypertension (32%, n = 24/76), aortic valve stenosis (19%, n = 7/76), or wild-type amyloidosis (16%, n = 6/76). Conclusion: One-third of patients with ICD-10 codes for HCM or HOCM did not fulfil recognized diagnostic criteria. Incorrect diagnosis of HCM may cause unnecessary family investigations, which may be associated with anxiety, and a waste of healthcare resources. This highlights the need for specialized cardiomyopathy services to ensure correct diagnosis and management of HCM.